Lookback — a user testing app that was co-founded in Sweden first as a side project by Spotify engineers before striking out on its own with funding from Index and others — has made its first acquisition: it has acquired a UK startup called Reissued, the company behind screencasting app QuickCast, which had 15,000 users and 500,000 screencasts recorded on its platform, from customers that include the likes of Twitter and Basecamp.